Cancers are diseases that account for the leading cause of death. The current treatment thereof consists principally of surgical therapy, which may be combined with radiation therapy and/or chemotherapy. In spite of the development of novel surgical techniques or the discovery of novel anticancer agents in recent years, the existing treatment of cancers has an insufficiently improved outcome, except for some cancers. With advances of molecular biology or cancer immunology, antibodies that specifically react with cancers, cancer antigens that are recognized by cytotoxic T cells, genes encoding such cancer antigens, and the like have been identified in recent years, raising expectations on specific cancer therapy targeting the cancer antigens.
Cytoplasmic-activation and proliferation-associated protein 1 (CAPRIN-1) has been known as an intracellular protein that is expressed upon activation or cell division of resting normal cells and forms cytoplasmic stress granules with intracellular RNAs to participate in the regulation of transport and translation of mRNAs. This protein has been found to be specifically expressed on the surface of cancer cells and is under study as a target of antibody drugs for cancer treatment (Patent Literatures 1 to 19).